Electrical apparatus



Aug 30, 1949- c. G. MQNTGOMERY ELECTRICAL APPARATUS INVEN'TOR Filed April 2e, 1944 @www "mill-lm Patented Aug. 30. 1949 ELECTBIEAL APRARA-'EUS Carol G. Montgomery, Belmont, Mass.assignor,

liy mesne assignments, to the'Unted" States of' America .as represented bythe Secretary of War ApplicaticnApril-ZS, 1944Serial No. 53258.61

' (orare-39)' 3 Claims. 1

This `invention relates to an electrical apparatus andl more particularly toa detachable holder for a gas discharge type. switch. The switchinvolved comprises a cavity resonator wherein switch operation results from achange inA electricalcondi.- tion` in the resonator. Such a change initiates a discharge across a gap therein which causes the resonator to become detuned, and consequently non-conducting. In1 this manner a circuit/beyond the switch is electrically isolated from other `parts of an associated system.

A switch of this character finds particular ap.- plication in a radio-echo detection system whereinra transmitter anda receiver are locatedin close proximity to each other. In sucha system it is customary to pulse a transmitterat fixed intervals and utilize received echo pulses for determination of target data. A detection system. of this character .have separate transmitter and receiver antennae, or it may utilize, a common antenna. Regardless or the type'of antenna systern used, the amount of power. radiatedftrom. the antenna during transrnitter operation is extremely large in comparison to the amount of power necessary and desirable for receiver operation. I-hus there is a problem of protecting the rem ceiv-er., particularly the crystal detectors therein, lfrom excessive energy input during transmitter operation. The present switch functions to disconnect the receiver from the antenna during `transmitter operation. and then re-establish. the connection during the intervals between transmitter operation.

A protective switch of this.. character. is shown and described but not claimed in the co-pending application of Harold K. Farr, Serial Number 488,098, led May 22,1943.

In the usual radio-echo detectionsystem, very high radio frequencies generally are used. At these highrecuencies, it is customary to use hollow Wave guide type transmission lines. The present switch is adaptedfor use in suona hollow Wave guide transmission system. VInthe following discussionV it is assumed that. a common an.- tennais used bothfor transmission=-and reception, although. of. course, the invention'would be applicable to a two er more antenna system.

The linstant switch comprises a highly tuned cavity resonator disposed Within andforming a ypartof the wave guide transmissionv line which .connectsthe receiver to the antenna. The reso.- nator is embodied in a gas-nlled. breakdown type discharge tube mounted in the Wave guide.V 'Ine tube has a direct currenty biasV potential which :maintains anl electric field.. in the .tube at. avalue just below .that at. which conduction may take place.` During transmitter operation, the high intensity energy pulse suiciently increases the iieldlso. that a discharge occurs. As a result, the

v resonator is cle-tuned for they operating frequency andthe receiver is effectively disconnected from the system. At the Vconclusion of the pulsar-onduction ceases. andthe resonator again becomes tuned, whereby echo pulses received by the antennamay be communicated .to the receiver.

The operation. of the switch depends upon the factthat a gaseousdischarge Will occur at a predetermined.small.potentialA above the direct current. bias potential. The operating characteristic of. any gas discharge device gradually changes with .time due Vto a phenomenon, known as sput=n tering,.which.occ11rs:at the tube electrodes. Sputtering,gene1ally caused by positive ion bombardment,A results in the deposit of metallic electrode particles on the tube walls. This is particularly harmfulin the present instance wherein the tube constitutes a cavity resonator, because the resonant frequency thereof will change as metall is sputtcredonthe tube walls. Also, gas Within the tube. is occluded by the sputtered electrode particles with the result that in time, gas pressure decreases to .a point where the tube becomes inoperative, or at least inoperative at the potentials used.. Since failure of the tube to operate properly Willresult in a surge of high power into the receiver.. considerable damage may result by reason ofi these. changed operating characteristics. Therefore, it is .necessary to provide a simple meclrianical structure for the ready removal and replacementv of such a gas tube. Ilhe principal object or theinvention, therefore. is to provide such a structure.

.In the.,draWing,.Fig. 1v is a sectional View of the vinventions-Fig. 2 is a sectional View onz the line 2 2 otFig. 1,.and-.Fig.,3 is a sectional exploded View showing details of the detachable Vtube mounting structure.

' Referrinrgr now to Fig.. l, rectangular wave guide 5l extends between a transmitter and an antenna. A' second rectangular wave guide `6 extends at right angles from. guide 5 through aprotective switch., generally indicated by l, to a receiver. .Guides .5 and 6 vmay be coupledl together in any usual` mannena chokestructure preferably being .provided .to avoid .radiation losses. Thus wave guide 5-hasrigidly fixed thereto a circularstructurefhaving an annular channel 9 and avange HIL.. The adjacent endzof guide ii hasacooperating :circular Ilange.Y it, theY outer. portion thereof 1 being:secured lto-ilange filthy screws-12. Structure 8 has a rectangular central opening aligned with and forming a part of wave guide 6. There is a small clearance I3 between the main body of structure and flange II, clearance I3 extending between annular channel 9 and the space within the guide. Channel 9 is of proper depth to constitute a quarter wave choke to prevent radiation loss at the joint. A similar joint, generally indicated by !4, may be provided on the opposite side of switch 1.

Referring now to switch 1, wave guide 6 is provided with aligned circular openings in its opposing wide sides I and I6. An annular metallic sleeve I1 is snugly received in said circular openings, a portion I8 thereof being provided at the top to overlie side I5 around its opening. Sleeve I1 is rigidly iixed to guide 6, as for example by solder, to provide a good electrical connection` therebetween. The inner surface I9 of sleeve I1 is tapered from a wide diameter at the top within portion I8 to a narrower diameter at the end associated with opposite side I6. Portion I8 has a shallow radial slot adapted to receive an aligning pin carried by a later described member of the switch assembly.

A tube-carrying metallic sleeve 24 has its exterior surface tapered as shown at 25 for cooperation with the tapered interior surface of sleeve I1. Sleeve 24 is adapted to be received within sleeve I1, the tapered surfaces thereof cooperating to properly position sleeve 24 and associated tube within sleeve I1, and to provide good electrical contact therebetween. The interior cylindrical surface of sleeve 24 has two inwardly extending annular flanges 26 and 21, said anges comprising supporting contacts for the later described gas discharge tube. Sleeve 24 extends somewhat beyond the ends of sleeve I1, the ends of sleeve 24 being threaded as shown at 28 and 29. Sleeve 24 is split as shown in the drawing so that the sleeve may be circumferentially expanded to receive the tube. A small circular aperture 29a (Fig. 3) is provided in sleeve 24, preferably at the split, for alignment with slot 2D in sleeve I1. If desired, sleeve 24 may be split in two places instead oi" one, registering means being provided on the two sections to permit accurate assembly.

Sleeves I1 and 24 have -portions aligned with wave guide 6 cut away to provide transverse channels, generally indicated by 36 and 3 I, these channels constituting portions of Wave guide communicating with the associated cavity resonator. The two sleeves have additional aligned portions cut away to provide opposed circular openings 32 and 33 (best shown in Figs. 2 and 3) which cooperate with means later described for tuning the resonator.

A gas-lled discharge tube 35 is carried within sleeve 24. Tube 35, Well known in this art, includes two oppositely disposed horn-shaped electrodes 36 and 31, the narrow ends of the horns being spaced to provide a discharge gap 38 Within glass tube envelope 39. The aring ends of the horns extend through envelope 39 and terminate in annular flanges 40 and 4I which are received on anges 26 and 21, respectively, of sleeve 24. As will be understood, sleeve 24 is expanded circumferentially at the slit to permit mounting of the tube within the sleeve. Tube 35 hasa keep-alive electrode 42 terminating adjacent gap 38 within electrode 31, electrode 42 being connected through lead 43 to -a suitable source of D. C. bias voltage. The oppositely disposed electrodes 36 and 31 cooperate to define an annular cavity resonator which, during the time the resonator is in tuned condition, functions somewhat as a. one-to-one transformer in wave guide 6. The resonator is positioned in guide 6 at a point generally a half wave length distance from the junction of guide 6 with guide 5. Thus, impedance lconditions existing at the resonator will be reflected to the junction. When the resonator impedance is low (resonator is tuned) a low impedance exists at the junction to direct Iantenna energy to the receiver. Conversely, when resonator impedance is high (as occurs with a resonator de-tuning discharge during transmitter operation) a high impedance exists at the junction in the direction of guide 6 whereby little if any energy passes to the receiver.

Flange 4I of electrode 31 is maintained in position on supporting flange 21 by a retaining sleeve 45, which snugly telescopes sleeve 24 and bears on flange 4I. A positioning pin 46 is carried by sleeve 45, pin 46 extending through aligning aperture 29a in sleeve 24 and being received in radial slot 20 of sleeve I1. Pin 46 provides for proper alignment of the various members of the assembly. Retaining sleeve is reduced in section at its end to provide a shoulder 41. A ring nut 50 is removably associated with threads 29 of sleeve 24, nut 50 having a bearing portion 5I adapted to engage shoulder 41 of sleeve 45. A somewhat similar structure is provided at the opposite end of sleeve 24 wherein a second retaining sleeve telescopes sleeve 24 and bears against iiange 4U of electrode 36 to maintain said ange in position on supporting flange 26. In both instances, the electrode and supporting flanges provide electrical as well as mechanical connections for the tube. An annular nut 56 is detachably associated with threads 28 at the lower end of sleeve 24, nut 56 being adapted to bear against the lower end of sleeve I1 to lock the detachable tapered sleeves in predetermined position. Another nut 51, threaded into nut 56, bears against sleeve 55 to retain said sleeve in position against electrode iiange 4i).

Referring to Fig. 2, a system for tuning the cavity resonator is associated with the above described assembly and disposed at right angles to the axis of Wave guide 6. This system comprises two symmetrical units generally indicated by 59 and 60. Referring to the unit 60, a circular openn" ing is provided in the narrow side of guide 6 in aligned relation with circular opening 33 in the' tube-mounting assembly. An internally threaded sleeve 6I is associated with the guide side at the circular opening, a reduced section 62 thereof extending into the guide and bearing against the aligned portion of sleeve I1. An adjusting nut 63, threaded into sleeve 6I, carries at its reduced end 64, a plunger 65. Plunger 65 is adjustable to accurately tune the resonator. Detailed description of symmetrical unit 59 is unnecessary, it being sufficient to say that tuning is best accomplished by adjusting both units.

The above described assembly provides for easy removal and replacement of gas discharge tube 35. This readily is accomplished by first removing nuts 51 and 56, respectively, at which time sleeve 55 will d rop out to free the lower tube electrode. Next, the remaining assembly within tapered sleeve I1 may be removed from the sleeve. Nut 5D releases retaining sleeve 45, which is removed by expanding sleeve 25 to permit disengagement of the aligning pin 46. Sleeve 25 may be further expanded to permit removal and replacement of the tube. Reassembly is easily accomplished by reversing the above procedure.

The tapered surfaces of the two sleeves cooperate to position the tube properly within guide 6, the bearing surfaces therebetween providing a rm, electrical contact between the tube and the guide.

Having thus described the invention, what I claim' as new and desire to secure by Letters Patent is:

1. A holder for a breakdown type of gas discharge tube, said holder comprising a metal body having a transverse channel therethrough forming a portion of a wave guide, said body having an elongated channel longitudinally thereof and perpendicular to said wave guide channel, said longitudinal channel being receptive to a removable and replaceable gas discharge tube, said body being separable into two parts lengthwise thereof, said two parts having means including tapering and apertured telescoping portions for assembling said two parts with the tube clamped in accurately predetermined position in the transverse channel.

2. A hollow wave guide, and means for detachably holding a breakdown type gas discharge tube in position in said hollow wave guide, said means including a hollow metallic body extending through said wave guide, said body being separable into two parts lengthwise thereof, the said two parts having intertting tapering telescopic clamping portions to intert and clamp said gas discharge tube therebetween.

3. A wave guide and a device to support a gas discharge tube transversely within said wave guide, said device comprising a first internally tapered metallic sleeve disposed transversely of said wave guide and diametrically apertured in alignment therewith; a second metallic sleeve externally tapered and apertured complementary to said first sleeve and having flanged surfaces formed integral therewith to engage said tube, said second named sleeve further being transversely split forming a pair of circumferentially expandable, resilient, tube engaging arms; a pair of metallic retaining Sleeves longitudinally displaceable within said second named sleeve to press said tube against said flanged surfa-ces; and longitudinally displaceable metallic members threadedly coupled to said second sleeve and frictionally coupled to said retaining sleeves to position said second named sleeve, said retaining sleeves and said tube within said first named sleeve.

CAROL G. MONTGOMERY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,615,468 McDonald Jan. 25, 1927 2,129,713 Southworth Sept. 13, 1938 2,415,962 Okress Feb. 18, 1947 2,427,089 Clifford Sept. 9, 1947 2,445,445 Marcum' July 20, 1948 FOREGN PATENTS Number Country Date 177,345 Great Britain Mar. 30, 1922 

